added unit tests for bigint

tests/test_smatrix.nim

@@ -4,7 +4,7 @@ from mmath/smatrix import det, lu, lup, lu_det, lup, det, from_pivot, invert, id
     newSMatrix, SMatrix, clone, tril, triu, lu_solve, `$`, `*`, `-`, `+`, `-=`, `+=`, `==`, `*`, norm2, newSMatrixFromArray,
     gauss_jordan_high, gauss_jordan_low, transpose, squared_norm2
 from mmath/svector import buildSVector, `-`, abs, norm, Svector
-from mmath/pivot import SingularMatrixError
+from mmath/error import SingularMatrixError
 from mmath/rational import newRational, Rational, one, zero, abs, `>`, `<`, `==`, `*`, `+`, `-`, `/`, `/=`, `+=`, `sqrt`
 import unittest
 
@@ -116,3 +116,4 @@ suite "Nim linear algebra library":
             let mtx = newSMatrixFromArray[2, 5, int]([1,4,8,2,5,7,3,6,9,0])
             let xpose = newSMatrixFromArray[5, 2, int]([1,7,4,3,8,6,2,9,5,0])
             check(mtx.transpose() == xpose)
+